This invention relates to gas valves, and particularly instant-on type gas valves.
Because of environmental concerns and emissions laws and regulations, manufacturers of motor vehicles are searching for a clean burning and cost efficient fuel to use as an alternative to gasoline. Natural gas is one candidate for such a purpose, and many vehicles have been converted to natural gas as a fuel source. Typically, the natural gas is stored on board the vehicle in compressed form in one or more pressurized cylinders.
Gas flow from such pressured cylinders are controlled by valves. One major concern is the vulnerability of such gas valves to crash damage. If the vehicle is involved in an accident, the gas valve must not fail in an unsafe or catastrophic manner. To this end, internally-mounted gas valves have been designed to mitigate such unsafe or catastrophic conditions. Examples of such valves are disclosed in Wadensten et al., U.S. Pat. No. 4,197,966, Wass et al., U.S. Pat. No. 5,197,710, and Borland et al., U.S. Pat. No. 5,562,117.
Although both Wass and Borland disclose internally-mounted gas valves, these gas valves suffer from the fact that they are relatively slow in opening when downstream pressure is relatively low. Further, although the gas valve disclosed in Wadensten can be characterized as fast opening relative to the gas valves disclosed in Wass and Borland, Wadensten""s valve design is complicated, requiring a relatively large number of components. Further, Wadensten""s valve cannot be used for tank filling operations through the same tank nozzle, thereby necessitating a further nozzle in the associated tank for filling operations.
In one broad aspect, the present invention provides a flow control valve for controlling gas flow comprising a conduit including a first conduit orifice, a second conduit orifice, and a third conduit orifice, a primary piston, disposed within the conduit, including a primary piston valve configured to seal the third conduit orifice, a first aperture and a second aperture, and a bore extending from the first aperture to the second aperture, and configured to facilitate communication between the first aperture and the third conduit orifice, a sealing member, interposed between the conduit and the primary piston, and configured to prevent gas from flowing within the conduit between the first conduit orifice and the second conduit orifice and between the first conduit orifice and the third conduit orifice, and a secondary piston, disposed within the conduit between the primary piston and the first conduit orifice, including a first valve, configured to seal the first aperture of the primary piston, and a second valve, configured to seal the first conduit orifice.
In another aspect, the present invention provides a valve as described above, wherein the primary piston is moveable, relative to the conduit, from a first primary piston position to a second primary piston position, and wherein the third conduit orifice is sealed by the primary piston valve when the primary piston is in the first primary piston position, and wherein the third conduit orifice is in communication with the second conduit orifice when the primary piston is in the second primary piston position.
In another aspect, the present invention provides a valve as described above, wherein the secondary piston is moveable, relative to the conduit, from a first secondary piston position to a second primary piston position, and wherein the first aperture of the primary piston is sealed by the first valve when the secondary piston is in the first secondary piston position, and wherein the first conduit orifice is sealed by the second valve when the secondary piston is in the second secondary piston position, and wherein the primary piston assumes the second primary piston position when the secondary piston is in the second secondary piston position. In a further aspect, the present invention provides a valve as described above,
In yet another aspect, the present invention provides a valve as described above, wherein the primary piston includes a valve seat and the first aperture is formed within the valve seat, and wherein the first valve is configured to sealingly engage the valve seat when secondary piston is in the first secondary piston position.
In a further aspect, the present invention provides a valve as described above, wherein secondary piston is biassed towards the first secondary piston position by a resilient member.
In a further aspect, the present invention provides a valve as described above, further comprising a solenoid configured to actuate movement of the secondary piston.
In a further aspect, the present invention provides a valve as described above, wherein the secondary piston is comprised of material which is responsive to electromagnetic fields.
In a further aspect, the present invention provides a valve as described above, wherein the secondary piston is comprised of magnetic material.
In a further aspect, the present invention provides a valve as described above, wherein the first aperture defines a first primary piston orifice, and wherein each of the first primary piston orifice and the first conduit orifice is characterized by a smaller cross-sectional area than the third conduit orifice.
In a further aspect, the present invention provides a valve as described above, wherein the first conduit orifice is characterized by a smaller cross-sectional area than the first primary piston orifice.
In a further aspect, the present invention provides a valve as described above, disposed within a pressure vessel.
In a further aspect, the present invention provides a valve as described above, coupled to a nozzle of the pressure vessel.
In a further aspect, the present invention provides a valve as described above, wherein the pressure vessel is characterized by a storage volume, and wherein each of the first conduit orifice and the second conduit orifice is in communication with the storage volume.
In a further aspect, the present invention provides a valve as described above, wherein the primary piston is comprised of a first part and a second part, wherein the second part is disposed remote from he third conduit orifice relative to the first part, and wherein the first part comprises non-magnetic material and the second part comprises magnetic material.
In a further aspect, the present invention provides a valve as described above, wherein the second conduit orifice is interposed between the first conduit orifice and the third conduit orifice.
In a further aspect, the present invention provides a valve as described above, wherein the sealing member is interposed between the first conduit orifice and the second conduit orifice.
By fitting the primary and secondary pistons within a single sleeve, the number of components and, therefore, the complexity of the structure is appreciably reduced. Further, the provision of a biasing means to bias the secondary pistons to close flow out of the valve permits use of passages provided within the valve for tank filling operations, thereby eliminating the requirement of a separate nozzle being provided in the tank and dedicated for filling operations.